
<div>001</div>
<div>002</div>
<div>003</div>

<script>
    // 匿名函数
    let test = 1
    ;(function(window,undefined){
        function init (el){
            let els = document.querySelectorAll(el)
            for(let i = 0; i < els.length; i++){
                this[i] = els[i]
            }
            this.length = els.length
        }

        let jQuery = function(el){
            return new init(el)
        }

        jQuery.extend = function(object){
            for(let key in object){
                init.prototype[key] = object[key]
            }
        }

        init.prototype = {
            css(cssAttr,cssVal){
                for(let i = 0; i<this.length; i++){
                    this[i].style[cssAttr]=cssVal
                }
                return this
            },
            ajax(options){ },
            attr(options){ },
            addClass(options){ },
        }
        window.jQuery = window.$ = jQuery
    })(window)

    $.extend({
        bg(){

        }
    })
    console.log($('div'));
    
</script>